The newcomer has joined our them team last month. It reminded me that of when I joined the company for the first time.
Then, I had a mixed feelings. I just felt both pleasant and not pleasant unpleasant at the same time like happy, a bright future, worry, and tension about the job. But I had confidence in myself because I am very diligent, talented, and promising about in sales part. I know if someone hears what I said earlier, they would say that it's a pretty surreal story and it is easier said than done. But no doubt, I can make it well.

REVISED:

The newcomer has joined our team last month. It reminded me of when I joined the company for the first time.
Then, I had mixed feelings. I just felt both pleasant and unpleasant at the same time like happy, a bright future, worry, and tension about the job. But I had confidence in myself because I am very diligent, talented, and promising in sales part. I know if someone hears what I said earlier, they would say that it's a pretty surreal story and it is easier said than done. But no doubt, I can make it well.

Hi Tony, 

Thanks for this as you wrote a relevant story and expressions as you used appropriate words and expressions here. Please take note of the following corrections to avoid the same mistakes. In a nutshell, all I can say is that you have a  determination and courage to think outside the box and extend your learnings. 

Teacher Neiz